The 2007 aggregate healthcare expenditures attributed to osteoarthritis (OA) treatment in the United States were $185 billion, with an average out-of-pocket expense for an OA patient of approximately $2600 annually (the equivalent of 3 wks pay for an average American citizen). Moreover, the OA patient population is anticipated to grow from 27 million patients to 67 million patients in 2030, due to an aging US population and an epidemic of obesity. Despite this significant and growing socioeconomic burden, disease modifying OA drugs (DMOADs) have been difficult to translate from the lab to the clinic. The lack of DMOADs is due in part to an inability to detect early-stage OA, a disease stage where interventions and lifestyle changes have greater potential to reverse a chronic cascade of joint destruction found in the OA-affected joint. Clinically, OA is diagnosed through radiographs and physical exams, yet these diagnostics are relatively poor at detecting early-stage OA. A significant need exists for technologies that facilitate early-stage OA diagnosis. Molecular biomarkers have tremendous potential to diagnose OA prior to the development of structural damage in the joint (pre-radiographic). The goal of this proposal is to develop a novel magnetic nanoparticle-based technique to collect OA biomarkers from synovial fluid without the need to remove fluid from the joint space. Using magnetic harvesting, potential molecular markers of joint destruction can be removed from the synovial fluid and quantified to examine the severity of joint disease. Moreover, because the technique can work in a wide range of joint fluid volumes, biomarkers could be quantified in both preclinical rodent models of OA and in the clinical setting. The proposal goal will be achieved through two specific aims. Aim 1 is to develop an enhanced, quantitative technique (magnetic harvesting) for the joint-level collection of OA biomarkers in vitro. Aim 1 will be achieved through three sub-aims: 1) Define key parameters for magnetic harvesting in vitro, 2) Investigate and experimentally verify models to relate the amount of biomarker collected via magnetic harvesting to the initial biomarker concentration within synovial fluid, and 3) Assess the sensitivity of magnetic harvesting in a phantom human knee. Aim 2 is to collect and analyze joint-level biomarkers in a rat model of knee OA using magnetic harvesting. Aim 2 will examine the utility of magnetic harvesting as a research tool for small animal models, comparing magnetic harvesting to other available methods to recover joint-level proteins for molecular analysis (lavage, fluid wicking). The immediate impact of this work will be the development of an innovative research tool that will enable the quantitative assessment of multiple joint-level molecular biomarkers in small animal models of OA. The long-term impact of this work is the potential to develop new methods to diagnosis early-stage OA and the development of a technology that would enable biomarker analysis in smaller human joints affected by OA, including the metacarpophalangeal and interphalangeal joints of the hand and the facet joints of the spine.